<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
    <title>Document</title>
</head>
<body>
    <div id="app">
        <button @click="count++">修改count</button>
        <button @click="unWatch">取消</button>
        <p>{{count}}</p>
    </div>
    <script>
        Vue.config.productionTip = false

        const vm = new Vue({
            el:'#app',
            data(){
                return{
                    count:0
                }
            },
            methods:{
                unWatch:() => {},
            }
        })

        vm.unWatch = vm.$watch(
            'count',
            function(){
                console.log('count改变了')
                console.log(this)
            },
            {
                deep: true,
                immediate: true
            }
        )
    </script>

</body>
</html>